1. Field of the Invention
The invention relates generally to isolation valves and more specifically to such valves in which a positively sealed isolation valve and a flow control valve are combined within a single housing.
2. The Prior Art
In the prior art it has been common in applications where fluid under pressure is to be quickly moved from one point to another, such as spacecraft propulsion systems, to provide a fast operating valve device to open flow paths for the fluid. In many instances a positive seal between the source of fluid under pressure and the outlet is also required to preclude fluid leakage until use is required. In the prior art, the operation of such positive seal valves has commonly occurred by utilization of pyrotechnic devices such as explosive charges, or alternatively through a source of gas under high pressure and in some instances through manual means. The utilization generally of pyrotechnic devices generates undesired products of combustion which may be detrimental. Sources of gas under pressure themselves require means for releasing the gas which in turn may necessitate the utilization of secondary explosive squibs or the like. Manually operated devices necessitate access to the structure to operate the manual apparatus, which in many instances, for example, space craft, is not normally possible.
Examples of prior art devices known to applicants are shown in U.S. Pat. Nos. 3,431,731, 3,620,237, 3,797,805, 3,903,914, 4,149,555, 4,181,139 and 4,244,386.